Function: rnfconductor
Section: number_fields
C-Name: rnfconductor
Prototype: GG
Help: rnfconductor(bnf,pol): conductor of the Abelian extension
 of bnf defined by pol. The result is [conductor,bnr,subgroup],
 where conductor is the conductor itself, bnr the associated bnr
 structure, and subgroup the HNF defining the norm
 group (Artin or Takagi group) on the given generators bnr.gen
Doc: given $\var{bnf}$
 as output by \kbd{bnfinit}, and \var{pol} a relative polynomial defining an
 \idx{Abelian extension}, computes the class field theory conductor of this
 Abelian extension. The result is a 3-component vector
 $[\var{conductor},\var{bnr},\var{subgroup}]$, where \var{conductor} is
 the conductor of the extension given as a 2-component row vector
 $[f_0,f_\infty]$, \var{bnr} is the associated \kbd{bnr} structure
 and \var{subgroup} is a matrix in HNF defining the subgroup of the ray class
 group on \kbd{bnr.gen}.
